Hello and welcome to the forum.
Use taskmanager startup tab
Check C:\ProgramData\Microsoft\Windows\Start Menu\Programs\StartUp
And
C:\Users\YourUserName\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup
and failing either or both of those look to these registry locations but of course back it up, create a restore point manually, and export the key prior to editing for safe keeping.
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Run
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
You can also use AutoRuns from SysInternals, which may also help locate the problem.
https://technet.microsoft.com/en-us/sysinternals/bb963902.aspx
Using the Windows Registry Editor can cause serious, system-wide problems that may require you to re-install Windows to correct them. It cannot be guaranteed that any problems resulting from the use of the Windows Registry Editor can be solved. If you choose to edit the Windows Registry please understand that you do so at your own risk so unless you feel fairly comfortable and confident you should probably not use the Editor. Changes made to the Windows Registry can take effect immediately and those that do not will take effect following the next reboot of your computer, and a current backup is not automatically made for you....So manually create a system restore point, backup the registry and export the key you are editing for safe keeping before doing so.